Casters which are commonly used on wheeled trucks and or transfer systems comprise a base plate, a yoke mounted for rotation on the base plate about a vertical axis with the yoke including a ring plate and spaced legs extending from the ring plate between which an axle is mounted and a wheel rotatably mounted on the axle. In certain uses of the wheeled trucks, it is desirable to lock the wheel in a predetermined circumferential orientation relative to the truck, for example, to cause the truck to move in a straight line or in an arch. Thus, it is common to provide a spring loaded plunger on the base plate which is urged into engagement with a notch or notches on the ring plate. In one type of caster swivel lock that is commercially used, the opposite end of the plunger is held in one of two axial positions by engagement of a cross pin on the plunger with either a shallow slot or a deep slot, the latter position corresponding to the notch engaging position. The operator must bend over and operate the mechanism by manually grasping and turning the plunger. Other similar mechanisms that have been proposed are shown in U.S. Pat. Nos. 1,633,638 and 2,068,160.
A problem with respect to such mechanisms is that in order to repair the lock mechanism, it is necessary to completely disassemble the mechanism or the entire caster and in the process of disassembly of the mechanism, there is a danger that the springs will be released causing injury.
Among the objects of the present invention are to provide a caster swivel lock construction wherein a removably mounted plunger assembly is provided that can be readily removed and replaced without injury; which construction is relatively simple and low in cost; and wherein the plunger assembly can be foot operated or hand operated by a motion of the foot or hand.
In accordance with the invention, the plunger is a part of spring loaded plunger assembly comprising a body, the plunger movable axially in the body, a spring associated with the plunger, a foot pad pivoted to said plunger on the other end and having a cam portion urged by the spring to engage a portion of the body so that the plunger is moved axially inwardly and outwardly by manipulation of the foot pad. The spring plunger assembly is removably mounted on the base plate so that the plunger axis extends radially inwardly toward the ring plate and movement of said foot pad causes said plunger to move radially inwardly and outwardly for engagement and disengagement with a notch. The cam portion has a configuration such that in one position of the foot pad, one end of said plunger is out of engagement with a notch, and in another position, the plunger is in engagement with a notch.